Fixture design for flexible led circuit boards

ABSTRACT

Techniques are disclosed for designing light fixtures for flexible LED circuit boards. The flexible LED circuit boards include an array of LED packages and the surface of the flexible circuit boards is highly reflective. A flexible LED circuit board may be shaped to conform to a rigid preform and the preform may be concave, convex, corrugated, or have any other custom shape. The shape of the preform, as well as the location of the LEDs within the flexible LED circuit may determine the light distribution of the light fixture. Alternatively, the lighting fixture may have multiple rods held in place with side plates and a flexible LED circuit board may be woven between the rods. A set of hole patterns in the side plates determine the location of the rods and the rods will determine the shape of the flexible LED circuit.

FIELD OF THE DISCLOSURE

This disclosure relates to lighting fixtures, and more specifically toflexible LED circuit board fixtures.

BACKGROUND

In lighting systems luminaires and LED arrays may be mounted usingvarious lighting fixtures. Once the lighting fixture is assembled, thelight distribution pattern it provides is typically fixed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flexible laminated LED circuit.

FIGS. 2 a-b illustrate two examples of flexible LED circuits fabricatedwith screen printed Ag ink on polyester including multiple LED stringsconnected in parallel.

FIG. 3 a shows a cross-sectional view of various LED package spacingsthat may provide different light distributions, according to anembodiment of the present invention.

FIG. 3 b shows a view from below of the flexible LED circuit fitted to acorrugated form, according to one embodiment of the present invention.

FIGS. 4 a-c collectively illustrate an example LED lighting fixture witha flexible LED circuit woven between rods, according to an embodiment ofthe present invention.

FIGS. 5 a-f collectively illustrate three LED package spacings alongwith their corresponding light distribution patterns, according tovarious embodiments of the present invention.

FIGS. 6 a-b show graphs of the light distribution coming from two pointsalong a sinusoidal shaped flexible LED circuit, according to twoembodiments of the present invention.

FIG. 7 shows an example flexible LED circuit including multiple LEDpackages woven between transparent rods, according to an embodiment ofthe present invention.

FIGS. 8 a-d illustrate various shapes and fixture designs for flexibleLED circuits, according to various embodiments of the present invention.

FIG. 9 illustrates a method for fabricating a light fixture for aflexible LED lighting circuit, according to an embodiment of the presentinvention.

DETAILED DESCRIPTION

Techniques are disclosed for designing light fixtures for flexible LEDcircuit boards. The flexible LED circuit boards include an array of LEDpackages or LED chips and the surface of the flexible circuit boards ishighly reflective, in some embodiments. In one example, a flexible LEDcircuit board may be shaped to conform to a rigid preform and thepreform may be concave, convex, corrugated, or have any other customshape depending on the desired light distribution pattern. In such anexample, the shape of the preform as well as the location of the LEDswithin the flexible LED circuit will determine the light distribution ofthe light fixture. Alternatively, the lighting fixture may have multiplerods held in place with side plates and a flexible LED circuit board maybe woven between the rods, in some embodiments. In such embodiments, aset of hole patterns in the side plates will determine the location ofthe rods and the rods will determine the shape of the flexible LEDcircuit. In some cases, the side plates may include multiple holepatterns and attaching the rods to different hole patterns will resultin different light distributions. The location of the rods as well ashow the flexible LED circuit is woven between the rods will determinethe final shape of the LED circuit within the lighting fixture.

General Overview

Flexible substrates with screen printed circuit patterns are used tofabricate flexible circuit boards. However, flexible LED circuit boardswith reflective substrates may be configured into multiple shapes andmay provide various light distribution patterns with the same physicalparts. Furthermore, different LED placements within a flexible circuitboard may provide different light distributions even if the shape of theflexible circuit is held constant. A lighting fixture may be designedthat takes advantage of these unique characteristics of a flexible LEDcircuit board.

Thus, in accordance with an embodiment of the present invention, alighting fixture is disclosed for housing a flexible circuit boardpopulated with an array of LED packages or LED chips. The flexiblesubstrate of the LED array may be a reflective material (e.g., PET), andthe circuit pattern may be screen printed onto the substrate, in someembodiments, which can reduce production cost as compared to standardcircuit boards or metal substrate boards. The flexible board may beshaped prior to being used in a light fixture, in some cases, and theflexible board may conform to a non-flat shape, in some embodiments.Such a design has a low input power density such that heat may bedissipated by convection and radiation and no heat sink is required. Inone embodiment, a flexible LED array with a reflective surface mayprovide customized light delivery with a fixed set of parts. Forexample, the same parts may be used to provide a highly directed lightsource or a dissipated light source depending on the contours of theflexible LED array and the spacing of the LEDs within the array.

In one example embodiment, a flexible LED array is placed against acurved preform and the LED linear arrangements may be either separatestrips with appropriate electrical connections or printed circuitpatterns on a large flexible sheet. The curved preform may be concave,convex, corrugated, or any other custom shape depending upon theintended light distribution. In some cases, the curved preform may be asection of PVC corrugated roofing material. In another embodiment, theflexible LED array may be laced between a number of rods and theplacement of the rods may customize the shape of the LED array andtherefore the light distribution. In one such example, the lightingfixture may include two side plates that hold the rods in place.

In some embodiments, custom screen printed circuits or LED arrays may bematched with the correct fixture configuration in order to achieve thedesired light distribution. The variations in shape and LED placementwould contribute to the final light distribution and could be customizedfor particular applications without major changes in parts.

Example Fixtures for Flexible LED Circuits

FIG. 1 shows a flexible laminated LED circuit. As can be seen, the LEDcircuit includes four copper ribbons and the upper laminate sheet hasmultiple perforations exposing portions of the copper ribbons for theplacement of the LED packages. The upper laminate sheet in thisparticular embodiment is transparent and the entire copper ribbons arevisible, while the lower laminate sheet has a reflective upper surface.In other embodiments, the upper laminate sheet may have a reflectiveupper surface. Although this particular example shows four copperribbons laminated between two sheets, other embodiments may includefewer or more copper ribbons and the copper ribbons may be replaced withcopper wires, or any other suitable conductive material. In some cases,the thin copper ribbon may be around 0.003 inches thick. The LEDpackages may be attached using a conductive epoxy or solder, in someembodiments. Because the LED packages are being attached to a metallicconductive wire (a copper ribbon in this example), solder may be used inorder to avoid the difficulties associated with conductive epoxies.

FIGS. 2 a-b illustrate examples of flexible LED circuit boards includingmultiple LED strings connected in parallel. As can be seen in theexample of FIG. 2 a, a flexible LED circuit may be fabricated withscreen printed Ag ink on a flexible substrate, in some embodiments. Thesubstrate could be, for example, PET or any other suitable flexiblesubstrate material. LED packages may be connected in series along theconductive traces to form multiple LED strings and the surface of theflexible circuit board may be reflective. FIG. 2 b illustrates theflexibility of the LED circuit board when it is rolled.

FIG. 3 a shows a cross-sectional view of various LED package spacingsthat may provide different light distributions, according to anembodiment of the present invention. As can be seen in this example, theflexible LED array is arranged in a corrugated shape and the top LEDpackage spacing has the LEDs near the crest of each corrugated wave,while the middle LED package spacing has the LEDs at the center of eachcorrugated wave, and the lower LED package spacing has the LEDs at thebottom of each corrugated wave. FIG. 3 b shows a view from below of theflexible LED circuit fitted to a corrugated form, according to oneembodiment of the present invention. The direct light path from the LEDpackages is shown. Such a corrugated shape could be readily used invarious area lighting applications including, for example, a dropceiling light fixtures with dimensions of 2 ft.×2 ft. or 2 ft.×4 ft.However, the lighting fixtures described herein could be designed forany area lighting application and the present invention is not intendedto be limited to any particular size or set of dimensions.

FIGS. 4 a-c collectively illustrate an example LED lighting fixture witha flexible LED circuit woven between rods, according to an embodiment ofthe present invention. In such an embodiment, the flexible circuit boardmay be mounted within a lighting fixture housing without being attachedto the surface of a rigid preform. Such a fixture may provide a moreversatile system whereby the “wavelength” and the “amplitude” of theshaped flexible LED circuit would be more customizable based on thelocation of the rods. The example LED circuit board in FIGS. 4 a-c hasthe LED packages placed such that they are near the crest of the circuitboard wave pattern. As can be seen in FIG. 4 a, the rods in this exampledefine the shape of the flexible LED circuit when the circuit is wovenbetween the rods. As can be seen in the example of FIG. 4 b, this designhas two side plates, each having hole patterns through which the rodsmay be placed. FIG. 4 c shows a view from below of the flexible LEDcircuit, and the direct light path from the LED packages is shown. Thedirection of the light from the LED packages may be changed, forexample, by changing the spacing and location of the rods.

FIGS. 5 a-f collectively illustrate three LED package spacings alongwith their corresponding light distribution patterns, according tovarious embodiments of the present invention. In these exampleembodiments, the light distribution is influenced by locating the LEDstrips at different points along the “curve” or “wave” of the corrugatedLED circuit (whether the circuit is attached to a corrugated preform orshaped using rods and side plates). FIG. 5 a shows the LED strips placednear the crest of the corrugated LED circuit and FIG. 5 b is a graph ofthe corresponding polar light distribution. FIG. 5 c shows the LEDstrips placed near the middle of the corrugated LED circuit shape andFIG. 5 d is a graph of the corresponding polar light distribution. FIG.5 e shows the LED strips placed near the bottom of the corrugated LEDcircuit shape and FIG. 5 f is a graph of the corresponding polar lightdistribution. The polar light distribution plots shown in FIGS. 5 b, 5d, and 5 f graph the light intensity in candelas (CD) and demonstratethat there is a significant difference in the light distribution patternfor each LED strip placement. As can be seen, therefore, the lightdistribution of a flexible LED circuit is customizable using the samebasic parts, depending on the location of the LED strips within theshaped LED circuit.

FIGS. 6 a-b show graphs of the light distribution coming from two pointsalong a sinusoidal shaped flexible LED circuit, according to twoembodiments of the present invention. In these example embodiments,non-diffused reflection is assumed for illustrative purposes. Theexample in FIG. 6 a shows the light distribution coming from a pointnear the crest of the sinusoidal LED circuit, while the example in FIG.6 b shows the light distribution coming from a point near the middle ofthe sinusoidal LED circuit. In one specific example embodiment, a flatarray of Lambertian LED packages may produce a Lambertian lightdistribution when used in a downward facing lighting application, asshown in these example embodiments. As can be seen when comparing theexample of FIG. 6 a with the example of FIG. 6 b, minor changes in theLED package locations would produce different light distributionpatterns other than a Lambertian distribution.

FIG. 7 shows an example flexible LED circuit including multiple LEDpackages woven between transparent rods, according to an embodiment ofthe present invention. In this particular example embodiment, the rodsare glass tubes and the side plates are ¼ inch aluminum plates having aparticular hole-pattern. In other embodiments, side plates may includemultiple hole-patterns and the user may configure the rod placement asdesired. In still other embodiments, a consumer may specify the type oflight distribution desired and the rod placement may be determined andthe circuit may be laced for the desired application. The rods could bemade of reflective material and may be fastened with setscrews or heldwith lock nuts on the end of threaded rods, in some embodiments. Therods may also be replaced with cables laced through the hole pattern andheld taught at the ends, in some embodiments. Such cables could be thinand coated with a reflective material.

FIGS. 8 a-d illustrate various shapes and fixture designs for flexibleLED circuits, according to various embodiments of the present invention.FIG. 8 a shows a flexible LED array attached to a concave down rigidpreform, while FIG. 8 b shows a flexible LED array attached to a concaveup rigid preform, and each LED circuit shape provides a specific lightdistribution pattern. FIGS. 8 c-d show a concave down configuration fora flexible LED circuit utilizing a rod and side plate configuration.FIG. 8 c is a cross-sectional view of the rod and side plate fixturewith the flexible LED circuit woven between the rods while FIG. 8 dshows the same configuration from below. Various shapes and heights maybe used for the rigid forms, and in some cases the flexible LED circuitmay be replaced with a new flexible LED board with the same or differentpattern and the fixture itself could remain the same. The variouspreforms and rod arrangements may be incorporated within a light fixturehousing, in some embodiments.

Methodology

FIG. 9 illustrates a method for fabricating a light fixture for aflexible LED lighting circuit, according to an embodiment of the presentinvention. The method may begin with determining 901 the desired lightdistribution. Once the desired light distribution is known, the methodmay continue with determining 902 the ideal circuit shape and LEDplacement in order to achieve the desired light distribution. Asdiscussed above, the light distribution may be manipulated by alteringthe shape of the flexible LED circuit as well as the placement of theLED strings within the LED circuit. The method may continue withdetermining 903 whether the flexible LED circuit will be fastened to arigid form. In some cases, the rigid preform may be concave, convex,corrugated, or any other suitable shape for achieving the desired lightdistribution. If the LED circuit will be fastened to a rigid form, themethod may continue with fabricating 904 the flexible LED circuit andthe rigid form. As discussed above, the shape of the preform as well asthe placement of the LED strings within the flexible LED circuit dependson the desired light distribution. The method may then continue withassembling 906 the light fixture housing, which may include attachingthe LED circuit to the rigid preform. If the flexible LED circuit is notto be attached to a rigid form, the method may continue with fabricating905 the flexible LED circuit and light fixture side plates with thedesired hole patterns or achieving the intended light distribution. Asdiscussed above, the hole patterns in the side plates are used forinserting the rods which will determine the shape of the flexible LEDcircuit. The method may then continue with assembling 906 the lightfixture housing, which in this particular case includes insertingtransparent or reflective rods into the holes of the side plates andweaving the flexible LED circuit between the rods.

Numerous embodiments will be apparent, and features described herein canbe combined in any number of configurations. One example embodiment ofthe present invention provides a lighting fixture. The lighting fixtureincludes a lighting fixture housing, and a rigid preform mounted to thehousing, the preform having a non-flat shape determined by a desiredlight distribution pattern produced when a flexible LED circuit isattached to the preform. In some cases, the rigid preform is concavedown when mounted to the housing. In some cases, the rigid preform isconcave up when mounted to the housing. In some cases, the rigid preformis corrugated. In some cases, the fixture includes the flexible LEDcircuit conforming to the shape of the rigid preform. In some suchcases, the flexible LED circuit has a reflective surface. In other suchcases, the spacing of LEDs within the flexible LED circuit is determinedby the light distribution pattern produced when the flexible LED circuitis attached to the preform. In some cases, the lighting fixture isconfigured to provide a customized light distribution pattern byattaching to the rigid preform flexible LED circuits having differentLED arrangements.

Another embodiment of the present invention provides a method offabricating a lighting fixture. The method includes determining adesired light distribution pattern, and fabricating a flexible LEDcircuit housing configured to hold a flexible LED circuit in a desirednon-flat shape, the shape being determined based on the desired lightdistribution pattern. In some cases, the housing for the flexible LEDcircuit includes a rigid preform and the shape of the preform isdetermined by the light distribution pattern produced when the flexibleLED circuit is attached to the preform. In some cases, the methodfurther includes fabricating the flexible LED circuit wherein thespacing of LEDs within the circuit is determined based on the desiredlight distribution pattern. In some such cases, the flexible LED circuithas a reflective surface. In some cases, the flexible LED circuithousing is configured to hold the flexible LED circuit in a concave downshape. In some cases, the flexible LED circuit housing is configured tohold the flexible LED circuit in a concave up shape. In some cases, theflexible LED circuit housing is configured to hold the flexible LEDcircuit in a corrugated shape. In some cases, the housing includes atleast two side plates to which the rigid preform is secured. In somecases, determining the desired light distribution pattern includesreceiving a desired light distribution pattern from a customer.

Another embodiment of the present invention provides a lighting fixture.The lighting fixture includes a lighting fixture housing having at leasttwo side plates. The method also includes a flexible LED circuit havinga reflective surface, and a rigid preform mounted to the at least twoside plates, the preform having a non-flat shape determined by a desiredlight distribution pattern produced when the flexible LED circuit isattached to the preform. In some cases, the spacing of LEDs within theflexible LED circuit is determined by the light distribution patternproduced when the flexible LED circuit is attached to the preform. Insome cases, the shape of the rigid preform is at least one of concaveup, concave down, or corrugated.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Many modifications and variations are possible in light ofthis disclosure. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

What is claimed is:
 1. A lighting fixture comprising: a lighting fixture housing; and a rigid preform mounted to the housing, the preform having a non-flat shape determined by a desired light distribution pattern produced when a flexible LED circuit is attached to the preform.
 2. The fixture of claim 1 wherein the rigid preform is concave down when mounted to the housing.
 3. The fixture of claim 1 wherein the rigid preform is concave up when mounted to the housing.
 4. The fixture of claim 1 wherein the rigid preform is corrugated.
 5. The fixture of claim 1 further comprising the flexible LED circuit conforming to the shape of the rigid preform.
 6. The fixture of claim 5 wherein the flexible LED circuit has a reflective surface.
 7. The fixture of claim 5 wherein the spacing of LEDs within the flexible LED circuit is determined by the light distribution pattern produced when the flexible LED circuit is attached to the preform.
 8. The fixture of claim 1 wherein the lighting fixture is configured to provide a customized light distribution pattern by attaching to the rigid preform flexible LED circuits having different LED arrangements.
 9. A method of fabricating a lighting fixture comprising: determining a desired light distribution pattern; and fabricating a flexible LED circuit housing configured to hold a flexible LED circuit in a desired non-flat shape, the shape being determined based on the desired light distribution pattern.
 10. The method of claim 9 wherein the housing for the flexible LED circuit comprises a rigid preform, the shape of the preform determined by the light distribution pattern produced when the flexible LED circuit is attached to the preform.
 11. The method of claim 9 further comprising fabricating the flexible LED circuit wherein the spacing of LEDs within the circuit is determined based on the desired light distribution pattern.
 12. The method of claim 11 wherein the flexible LED circuit has a reflective surface.
 13. The method of claim 9 wherein the flexible LED circuit housing is configured to hold the flexible LED circuit in a concave down shape.
 14. The method of claim 9 wherein the flexible LED circuit housing is configured to hold the flexible LED circuit in a concave up shape.
 15. The method of claim 9 wherein the flexible LED circuit housing is configured to hold the flexible LED circuit in a corrugated shape.
 16. The method of claim 9 wherein the housing comprises at least two side plates to which the rigid preform is secured.
 17. The method of claim 9 wherein determining the desired light distribution pattern comprises receiving a desired light distribution pattern from a customer.
 18. A lighting fixture comprising: a lighting fixture housing having at least two side plates; a flexible LED circuit having a reflective surface; and a rigid preform mounted to the at least two side plates, the preform having a non-flat shape determined by a desired light distribution pattern produced when the flexible LED circuit is attached to the preform.
 19. The fixture of claim 18 wherein the spacing of LEDs within the flexible LED circuit is determined by the light distribution pattern produced when the flexible LED circuit is attached to the preform.
 20. The fixture of claim 18 wherein the shape of the rigid preform is at least one of concave up, concave down, or corrugated. 